Key Engineering Materials Vol. 854

Abstract: Modern methods of machining of bed slideways with the required parameters of accuracy and quality of the processed surfaces are considered in order to increase productivity in the treatment of the surface of machine stands. To improve productivity, the finishing sanding operation has been replaced with finishing milling to ensure the required roughness, flatness and parallelism. The method of replacement of technological operations as exemplified by processing of a bed made of gray cast iron of grade “СЧ-20” is studied. The priority method of increasing the productivity of the processing of machine slideways of metal-cutting equipment, based on the use of cutting ceramics during the processing of the bed as a final technological operation, is determined. Based on the microstructural characteristics of oxide-carbide cutting ceramics, a uniform method of equipping cutters with cutting inserts with equal lifespan is used to increase productivity and achieve the required surface finish. This method of the milling cutter layout allows for longer life and provides the required margin of tool accuracy as well as allows predicting premature wear of the cutting tool. The results of the work are the identification of the patterns of influence of structural parameters of cutting ceramics on the quality of machine slideways of metal-cutting equipment in the selective formation of instrumentation. Studies have shown that the quality of machining depends on the microstructure characteristics of each insert used in the machining process when using interchangeable multi-sided oxide carbide ceramic inserts. The increase in productivity and quality of machining is achieved by monitoring the microstructure of the cutting oxide-carbide ceramics.

Abstract: The article covers a solution of a modern electronics problem: improvement of data transmission device speed using the example of fiber-optic communication lines (FOCL). The data processing rate and throughput of transmission channels are determined by capabilities of the optoelectronics and, first of all, by the performance of its hardware components. The article presents all possible ways to improve the performance of FOCL. Design and production of communication devices moves to the nanotechnological level that opens up new possibilities for creation of semiconductors with advanced characteristics. The methods and means chosen for production of the nanostructures are crucial for creation of the new generation hardware components. Graphene is considered as the most promising material for creation of the new generation hardware components for semiconductors. Potential capabilities of the material are not yet fully explored. Isotopic nanoengineering is used as the method for production of the nanostructures with improved characteristics. In particular, we use the neutron transmutation doping technology based on irradiation of a graphite sample with a neutron flux. This method increases content of the ¹³C isotope (natural graphite contains only about 1.1% of this isotope). As a result, the band gap opens bringing the properties of the material closer to the properties of a semiconductor. The closer the width of the graphene band gap to the width of the silicon band gap, the closer the properties of graphene to the properties of semiconducting silicon. Furthermore, all properties of the natural graphite (high throughput and sensitivity to almost the entire optical spectrum) are preserved.

Abstract: The present studies are devoted to studying the behavior of the nanopart during their interaction with the surface. Small additives in composite materials significantly increase their strength and other operational properties. When carrying out repairs in the oil and gas industry, it is promising to fill the detected cracks and crack-like defects with composite material, the distinguishing feature of which is high fluidity and penetration at the time of filling. After hardening, such composites must meet all the requirements for strength and durability. Such properties can be obtained using magnetic iron oxide nanoparticles. In the molding process, a balance must be maintained between the adhesive strength of the composite compound and its cohesive strength. For this, it is crucial to know the underlying mechanisms of the formation of thin films containing nanoparticles on the surface of various structural materials.

Abstract: It was found that at room temperature the value of the photoinduced current of Schottky diodes based on heterostructures InP/GaInAs/Pd at a hydrogen concentration of 0.03% is reduced by two orders of magnitude compared to the value without hydrogen. The value of the photoinduced current depends on the thickness of the depleted region on the surface of the semiconductor. A small change in the charged layer of H⁺ can cause a significant change in the thickness of this region and as a result, a strong change in the photoinduced current. This effect on current is much stronger than the influence of hydrogen concentration or capacitance without optical activation. As a result, it becomes possible to create hydrogen and hydrogen-containing gas sensors with much better sensitivity at room temperature. The original design of a miniature H₂ sensor including an IR LED, a Schottky diode with a Pd contact, a Peltier cooler and a thermosensor is demonstrated.

Abstract: Laser marking is a universal method of applying information to the products surface. Colored oxide films form on metal surface during a thermal exposure. The degree of steel heating influences the film thickness. Corrosion-resistant steel AISI 304 samples were laser-marked with a MiniMarker 2-20A4 precision laser complex. The contrast of the barcodes on a metal area depends on the surface roughness and the chemical composition of the steel. Fe₂O₃, Fe₃O₄ oxides forms the greatest contrast. RGB indicators are used to assess contrast. Study results may be applicable to increase the QR code contrast thereby contributing to the improvement of laser marking technology while preserving economic efficiency.

Abstract: Vanadium oxide films have been fabricated by the acetylacetonate and triethoxy vanadyl sol-gel methods on silicon substrates, as well as by magnetron sputtering on glass-ceramic substrates. Additional annealing in reducing atmosphere results in formation of vanadium dioxide or mixed phases with a VO₂ predominance. The obtained films demonstrate the metal-insulator transition and electrical switching. In the films produced from triethoxy vanadyl, the peculiarities of electrical properties are related to the size effect, heterophase character of vanadium oxide films, and different types of charge carriers in the bulk of nanocrystallites and on their surfaces. Also, the effect of doping with hydrogen by means of plasma-immersion ion implantation on the properties of vanadium dioxide is explored. It is shown that the transition parameters in VO₂ thin films depend on the hydrogen implantation dose. At doses exceeding a certain threshold value, the films are metallized, and the phase transition no longer occurs.

Abstract: The purpose of this study was to achieve a low-porosity HVOF (High velocity Oxygen Fuel) spray cover and to determine the effect of spray parameters on the porosity of the coating. The spray parameters studied include: Powder feed rate (A); Spray distance (B); Oxygen/Propane ratio to porosity of WC-12Co coating on 16Mn steel. Taguchi method and ANOVA (Analysis of variance) technique were used to optimize and analyze the effect of spray parameters. The results showed that the optimum spray parameters with A = 26 g/min, B = 0.2m, C = 5 for porosity smallest. Factor A has the greatest influence on porosity, followed by B and C. The experimental result is then compared to optimal results and the error is only 4.2 %. Hence, one can say that the optimal results are reliable and Taguchi method - ANOVA technique proved to be an effective solution to the optimization problem. Parameters for a WC-12Co coating with improved porosity on 16Mn steel substrate have been identified.

Abstract: Nowadays, thermal spray coatings are used to enhance mechanical properties of the material. One of the technologies used to produce thermal spray coating is HVOF spray technology. This is the most advanced and modern technology which has been widely used in the industry due to its flexibility and ability to create coatings with better adhesion in comparison with other thermal spray methods. This article presents some empirical findings from applying the 67Ni18Cr5Si4B alloy powder coating onto C 45 steel shaft by HVOF spray technology. It also analyzes the influence of some technological parameters on the adhesion of the coating. As a result, the parameters of HVOF spray technology are obtained suitable for recovering worn axis-sized workpieces.

Abstract: The results of the development of the flux CaO-Li₂CO₃-B₂O₃, operating in the oxidizing environment of the furnace, are shown. Flux is used to protect the melt from oxidation and removal of oxides from the coated sample surface. The use of this flux in open furnaces made it possible to apply high-quality nickel coatings with a thickness of 18 μm, which is comparable to the thickness of coatings obtained in vacuum furnaces in argon atmosphere. The negative effect of flux components on the sample surface was noted during prolonged contact under the conditions of the oxidizing environment of the furnace. Practical application of the research results will provide high-quality diffusion coatings on metal products. In addition, economic efficiency is maintained through accessibility of the equipment and flux components.

Abstract: Modern designs of piston rings of internal combustion engines and wear-resistant coatings used for them are considered. It is noted that the upper (compression) ring undergoes the most intense wear. Among the traditionally used wear-resistant coatings of compression rings, galvanic chrome plating and thermal spraying with molybdenum are most often used. The paper proposes the use of the ion-plasma spraying method for applying hard wear-resistant coatings to the working surface of piston rings based on titanium and molybdenum nitrides. The specified method relates to vacuum coating technologies (PVD methods), in which layers of high-strength materials are sprayed directly onto the surface of the product. The present work aimed to carry out comparative tribotechnical tests of piston ring samples having hard coatings obtained by ion-plasma spraying and to compare them with traditional galvanic chromium plating. A technique has been developed for a comprehensive assessment of comparative tribological characteristics, including the critical load during testing, the specific load of seizing, the coefficients of friction, scoring resistance, and wear resistance. The test results of samples with the galvanic coating with chromium, ion-plasma spraying with titanium nitride, and molybdenum nitride are shown. In contrast, it is shown that samples with an applied ion-plasma coating surpass samples that are electrolytically chrome plated by all tribological parameters. The results obtained allow concluding that the ion-plasma coating of molybdenum nitride is promising for piston rings, as well as other critical parts of internal combustion engines.